Many of the prior art methods and combinations of apparatus which are designed to accomplish optical waveguide amplitude modulation have intrinsically and inherently involved the reliance upon additional polarizer/analyzer devices for their operation. Generally, it may be said that many of such prior art methods and arrangements have relied upon giving effect to a polarization of light energy change which is induced in transmitted light in an optical waveguide or a bulk crystal device by either acousto-optic, magneto-optic, or electro-optic effects.
For example, optical waveguide switching and modulation has been proposed in the prior art as exemplified by U.S. Pat. No. 3,589,794 issued in the name of Enrique A. J. Marcatili on June 29, 1971. The optical waveguide amplitude modulation and switching functions achieved in this patent and many related prior art concepts was realized by the modification of resonant optical coupling between two parallel or closely contiguous optical waveguides.
Despite the fact that analogous coupled devices have been well known to operate satisfactorily in microwave technology applications, coupled optical waveguides depending upon resonance conditions inherently involve dimensional tolerances which are extremely critical for an efficient and effective operation at most optical wavelengths.
Although resonant coupling optical waveguide switching and modulation is relatively quite simple in concept, it's implementation is extremely difficult to realize through fabrication by practical and convenient techniques due to the extremely stringent tolerances required for it to function as a wholly effective device.
Accordingly, it is highly desirable that an optical waveguide interferometer modulator/switch be devised which inherently does not require the severely critical dimensional tolerances of prior art concepts and arrangements designed to be functionally equivalent in performing optical modulation and switching operations.